Primary brain involvement of disseminated histiocytic sarcoma in a Rottweiler dog – histopathology, 18F-fluorodeoxyglucose positron emission tomography and 7 T-magnetic resonance imaging findings: a case report

An eight-year-old, intact male Rottweiler dog was presented due to anorexia, lethargy, ataxia and imbalance. Cerebellar and thyroid masses were identified using 0.3T magnetic resonance imaging. The ¹⁸F-fluorodeoxyglucose uptakes of the masses were elevated on positron emission tomography and 7 T-magnetic resonance imaging fusion imaging. At 113 days after the initial presentation, new nodular lesions were observed in the skin, liver and spleen. Histopathology revealed multiple lesions of disseminated histiocytic sarcoma in the cerebellum, liver, spleen and skin, whereas the thyroid lesions were diagnosed as mixed medullary-follicular thyroid carcinoma. The primary site of the disseminated histiocytic sarcoma was found to be in the cerebellum. To our knowledge, this is the first case report to describe the imaging and histopathological findings of extracranial metastasis of a primary intracranial histiocytic sarcoma in a dog.